Damian Green will stand in for Theresa May at Prime Minister’s Questions (PMQs) on Wednesday, despite allegations that extreme pornography was found on his office computer. The first secretary of state is also being investigated over harassment claims.

With the inquiry “ongoing” – and with May on a three-day visit to the Middle East – Green will stand in at the most high-profile occasion of the parliamentary week. His appearance comes just days before his fate is to be decided by Sue Gray, the Cabinet Office’s head of propriety and ethics.

May’s spokesperson defended the decision. “The inquiry procedure is ongoing. Once it has concluded, it will report back and the findings will be made public. Damian Green is the first secretary of state and you would expect him to fill in for the prime minister at PMQs.”

Asked by the Independent if the appearance would “demean the office,” the spokesman replied: “There is an investigation that is ongoing, I’m not going to pre-empt that.”

Green has largely kept a low profile since the controversy broke. In early November, Tory activist Kate Maltby claimed he had touched her knee in 2015 and, one year later, sent her a suggestive text message. Earlier this month, he described the claims as “untrue [and] deeply hurtful.”

Allegations then surfaced that pornography of an “extreme” nature had been found on Green’s computer after a police raid in 2008. After the former Metropolitan Police commissioner, Sir Paul Stephenson, said he was informed that detectives had found such material, Green issued a statement in which he appeared to concede that porn had been found – but denied he had downloaded it or viewed it. In the statement, issued last week, he said: “As I have said throughout, I did not put or view pornography on the computers taken from my office.”

He says his porn accusers had “ulterior motives,” adding: “I reiterate that no allegations about the presence of improper material on my parliamentary computers have ever been put to me or to the parliamentary authorities by the police.”

May is desperate not to lose Green, having recently been forced to sack both Priti Patel, her international development secretary, and Michael Fallon, her defense secretary. As well as being a good friend over the past four decades, Green sits on around 20 cabinet committees, most of which he leads, making him a key player in determining Brexit strategy.

Downing Street has reportedly begun discussions on who could replace Green should he be forced to leave government. The frontrunners are understood to be Home Secretary Amber Rudd and Environment Secretary Michael Gove, who is known to be something of a protégé of media mogul and kingmaker Rupert Murdoch.